Vinylchloride monomer

The quality control of PVC, plasticizers, and additives must be done according to certain standards. In the case of making the blending material for medical uses, medical grade PVC, which contains <3 ppm vinylchloride monomers, should be used. 

Unlike bulk plastics and paper where unwanted substances can be removed by vacuum stripping (e.g. vinylchloride monomer from polyvinylchloride, styrene from polystyrene) or by washing (e.g. organic and metallic residues in mass-polymerised plastics), adhesives by their gummy nature are difficult to clean-up. Residues of incomplete polymerisation and reaction by-products could be effectively retained and may subsequently migrate. On the other hand, adhesives are generally not used in direct contact with the packaged foods. Rather, they are applied at seams and pack ends and any contact with the food is likely to be incidental and limited in area. 

In another investigation, ethylene oxide in polyvinylchloride was determined by dissolving 65 mg of sample in 1 ml of dimethylacetamide [189]. Headspace analysis was conducted on a glass column packed with Porapak T under isothermal conditions. The solvent was removed by back-flushing. An external standard was used for calibration. A vinylchloride monomer was also detected in this analysis (Figure 4.3). 

Directive on the list of simulants Directive on vinylchloride monomer (VCM)... 

A directive was adopted in 1978 regarding exclusively materials and articles containing free vinylchloride monomer (Directive 78/142/EEC). It lays down the maximum quantity of free monomer permitted in the finished article as 1 mg/kg and states that such materials and articles must not release to the foodstuffs with which they are in contact any amount of vinylchloride detectable by a method of analysis with a detection limit of 0.01 mg/kg. In 1980 and 1981 two further directives were adopted which lay down the method of analysis for vinylchloride in the finished article and in foodstuffs respectively (Directives 80/766/EEC and 81/432/EEC). 

Blends, L., Smith, P., Lawrie, B., Stephens, M.R., Evans, W.D. Portal hypertension in vinylchloride monomer workers. A hemodynamic study. Gastroenterology 1978 75 206-211... 

Machida, M-, Tanaka., Vinylchloride monomer production without pollution , Chem. Earn, and Engng Aer- (1L 100) 31 36 (1976). 

McPherson, R W., Starks, G Fryar, G. L, Vinylchloride monomer— What vouthould know . Hydrocar-... 

Multidimensional techniques of heart-cutting, cryotrapping, and back-flushing have been used to develop a capillary-based alternative to the packed-column techniques to determine residual vinylchloride monomer in PVC. This capillary-based method resolved some of the problems associated with the accuracy and reproducibility required for ultra-trace determination of this suspected carcinogen [52]. 

Vinylchloride monomer is used as intermediate for the production of polymers in a large number of production processes [13]. 

By supplying energy (heat), hydrogen chloride can be eliminated from the chlorinated hydrocarbon. For instance the splitting of HCl from 1,2 dichloroethane forms the vinylchloride monomer. 

Residual vinylchloride monomer from 0.02 to 0.1 ppm in PVC has been determined by gas chromatographic - mass spectrometric monitoring. ... 

The reason for the appearance of the dichlorospecies and the oligopropene is a very fast fi-chloride elimination reaction, which itself is much faster than the coordination and insertion of a further vinylchloride monomer. In the polymerization experiment with MAO, the chloro species can be realkylated by MAO either to produce further propene from vinylchloride or to oligomerize free propene to atactic oligopropene, respectively (Scheme 8). 

In the last three decades, membrane-based gas separation has become a well-established unit operation for a variety of important applications. Gas separation membranes operate in the chemical industry in hydrogen separation, monomer recovery, the enrichment of nitrogen from air, and natural gas treatment. Recovery of hydrogen from the purge gas of an ammonia reactor was established around 1980. Vinylchloride monomer recovery from the PVC production process was started up about 10 years later. Recently, the recovery of propylene from polypropylene purge bins became feasible. The removal of sour gases from natural gas as well as biogas operates reliably, today. ... 

For the formation of microgels the presence of a crosslinking monomer is not always necessary. Thus, microgels have also been detected in polymers prepared with bifunctional monomers, e.g. poly(acrylonitrile-co-vinylacetate) [39], polyethylene [40],poly(vinylchloride) [41] andpoly(vinylidenefluoride) [42].Obviously, the reason for the intramolecular crosslinking with the formation of microgels are side reactions. 

Vinyl-type addition polymerization. Many olefins and diolefins polymerize under the influence of heat and light or in the presence of catalysts, such as free radicals, carbomum ions or carbamons. Free radicals are particularly efficient in starting polymerization of such important monomers as styrene, vinylchloride, vinylacetate, methylacrylate or acrylonitrile. The first step of this process—the so-called initiation step—consists in the thermal or photochemical dissociation of the catalyst, and results in the formation of two free radicals-. 

Apart from trimethylborate, other trialkyl- and triarylborates, as well as alkylboron acids, are used. E.g., trialkylborates are good catalysts for the polymerisation of acrylonitrile, methylmethacrylate, styrene, vinylacetate, vinylchloride, vinylidenchloride, etc. The polymerisation of these monomers requires traces of oxygen. Oxygen seems to transform part of trial-kylborate into peroxide, which reacts with unoxidised trialkylborate and forms free radicals initiating polymerisation. 

SYNS CHLORETHENE CHLORETHYLENE CHLOROETHENE CHLOROETHYLENE CHLORURE de VINYLE (FRENCH) CLORURO di VINILE (ITALIAN) ETHYLENE MONOCHLORIDE MONOCHLOROETHENE MONOCHLOROETHYL-ENE (DOT) RCRA WASTE NUMBER U043 TROVIDUR VC VCM VINILE (CLORURO di) (ITALIAN) VINYLCHLORID (GERMAN) VINYL CHLORIDE MONOMER VINYL C MONOMER VINYLE (CHLORURE de) (FRENCH) WINYLU CHLOREK (POLISH)... 

The nomenclature of copolymers includes the names of the monomers separated by the interfix co-. Thus 1-25 would be poly(vinylchloride-co-vinyl acetate). The first monomer name is that of the major component, if there is one. This system applies strictly only to copolymers in which the monomers are arranged more or less randomly. If the comonomers are known to alternate, as in 1-26, the name would be poly(styrene-a//-maleic anhydride). Interfixes may be omitted when the name is frequently used, as in styrene-acrylonitrile copolymers (Section 1.5.3). 

In the same way, Matsushima et al. [44] prepared block copolymers from styrene, vinylacetate, vinylchloride and acrylic monomers with the following initiators ... 

In 1975, Csontos [92] working for the Goodrich Company, also studied the emulsion copolymeriration of a mixttire composed of two monomers Mj and Mj with xantho-gens and he investigated the hydrolysis of the xanthogen into the dithiol. Mj was partially soluble in water (greata" than 0.2%) e.g. various acrylates, VAc, allylic monomers, acrylonitrile and vinylchloride. 

Next to ethylene, propylene and vinylchloride, styrene is one of the most important monomers for the production of plastics. The worldwide demand for styrene in 1992 was 18.2 million tonnes and is expected to grow annually with 3-5% to 23.9 million tons in 2000 [42]. Recent production statistics show an annual production of about 1.3 million tons of styrene in the Netherlands. Approximately 75% of this is produced at DOW Benelux in Terneuzen by catalytic adiabatic dehydrogenation of ethylbenzene [42]. 

Manufacture. The monomer of polyvinyl Chloride is gas at room temperature and has a boiling point of -13.9 C. The monomer is manufactured in two ways (1) Acetylene and HCl gas are allowed to pass over active carbon and to react with each other at 150—200 C (2) chlorine gas is allowed to react on ethylene to produce C2H4CI2 (EDC) at 200 350°C to produce vinylchloride and HCl gas. These are separated by distillation. The monomer is then polymerized in a pressure vessel the mixture of water and liquid monomer is stirred violently. Benzoyl peroxide is used as a catalyzer and polyvinyl alcohol as a dispersion agent for the reaction. 

AG, and Nippon Oil Fats Co. Bulk amounts of styrene, vinylacetate, vinylchloride, ethylene, and numerous other monomers are produced worldwide by many petrochemical companies. 

Polymerization of unsaturated organic compounds (monomers) is a special type of chain reaction. In a process of breaking of multiple bonds, new monomers continuously attach to the radical or ionic chain carriers. An example of this is the cationic polymerization of vinylchloride into polyvinylchloride (PVC) ... 

Separation of low volatile organic components (VOCs) from gas streams through organophilic membranes, however, has become an accepted and widely used technology. Monomers like ethene, propene, or vinylchloride [23] are recovered from strip gas or waste gas streams and recycled to the upstream process. 

Just another step leads to the manufacture of one of the oldest monomers—vinylchloride—along with other vinyl derivatives (including acrylonitrile). 

The usual concentration of plasticizers is 20% to 40%, but some systems (plastisols) have 50% to 60% plastification. The diffusion of plasticizers impairs flexibility, making the polymer rigid and brittle. It is important to eliminate the use of toxic additives, which adversely affect the environment through contact with food stock or other polymers. For these reasons a liquid-phase plasticizer may be replaced by a solid-state plasticizer which is mainly based on a short-chain polymer (polyester or epoxy) or a long-branched one. The most ideal plastification may be achieved by an appropriate copolymerization. A typical example is a copolymer made from vinylchloride and vinylacetate, in which a low Tg monomer is inserted into the main chain. 

With the exception of the last example, the work of the McCarthy group can hardly be described as a chemical modification of a polymer. Muth et al. [64] applied the McCarthy blending method to the polymerization of the vinylic monomers styrene, methyl methacrylate, and methacrylic acid (MAA) inside scC02-swollen poly(vinylchloride), bisphenol-A polycarbonate, and poly(tetra-fluoro ethylene). In the case of the polymerization of MAA inside PVC, the PMAA generated inside the PVC host could not be completely extracted, and chemical grafting of PMAA onto the PVC could not be completely excluded. 

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